Open-hearth furnace



Patented Dec. 1, 1925.

PATENT OFFICE..

CALEB DAVIES, JR., OF POLAND, OHIO.

OPEN-HEARTH FURNACE.

' Application filed April 6, 1922. Serial No. 550,079.

To all whom it may camera:

Be it known that I, CALEB DAVIES, Jr., a citizen of the United States, and a resident of Poland, county of Mahoning, and State of Ohio, have invented a new and useful Improvement in Open-Hearth Furnaces, of which the following is a speeification, the principle of the invention being herein ex plained and the best mode in which I have contemplated applying that principle, so as to distinguish it from other inventions.

The modern open hearth steel furnace is a rectangular box-like structure enclosing a shallow hearth upon which the material entering into the manufacture of steel is melted and refined, .the necessary heat for the operation being supplied by a flame playing over such hearth. This flame is usually produced by the combustion of: gaseous fuel, which, together with the air necessary to support combustion, is supplied through large ducts located at either end of the furnace. poste ends of the furnace are ident ical :in

r size and shape, and are so arranged that the process may be reversed, the gas with the usual amount of air for combustion being alternately supplied, first in one end, then the other, and the products of combustion being drawn out at the opposite end.

The great majority of modern open hearth furnaces are fired with producer gas and considerable difiiculty is eX- perienced in adaptng the same for use with richer gases, such as coke oven gas and the like. The object of the present invention aecordingly is to provide an arrangement for introduoing coke oven or other gas into an open hearth furnace in such a way that even with an unusually small excess of air practically no unburned gas can reach the root, and at the same time no blowers and no stationary or removable constructions in passages for air or products of combustion will be required.

To the accomplishment of the `foregoing and related. ends, said invention, then, consists of the means hereinafter fully describe and particularly pointed out in the clains; the anneXed drawings and the following description setting forth in detail certain mechanism embodying the invention, such disclosed means constitut ing, however, but several of the various' mechan'cal The openings at the op-i forms in which the principle of the invention may be used.

In said annexed drawings Fig. 1 is a central longitudinal section through onexend of a typical open hearth furnace wherein the Construction has been modified for introduction of the gaseous fuel in accordance with my present improvement; Fig. 2 is a horizontal section of the same, the plane-of the section being indicated. by the line 2 -2, Fig. l; Fig. 8 is a vertical section of a detail taken on the same plane as that of Fig. `1 but on a larger scale; Fg. 4 is a view similar to Fig. 1, but illustrat ng a modification in construction; Fig. 5 is a vertical transverse section of such modified Construction, the plane of' the section being indicated by the line 5-5, Fig; tyFig. 6 is a horizontal plan view more or less diagrammatic in character of a furnace constructed in accordance with either of the 'foregoing designs and embodyingan additional'feature of improvement; Fig. T is a vertical transverse section of such lastmentioned Construction, the plane of the section being indicated by the line 7-7, Fig. 6; and Fig. 8 is a View similar to Fig. 7, but illustrating a modified form of such additional detail of Construction.

- In the Construction illustrated in Figs. 1,'

2 and 3 of the drawings I utilize the sta11dard type of producer-gas fired 'urnace, eX- cept that the gas ports and all partit ions between producer-gas and air passages are removed down to the upper part of the air and gas slag pockets 1 and ,2. An open vertical passage 3 is accordingly left, the upper end of which comnunicates through an unobstructed port opening l with the 'furnacechamber 5. As previously eX- plained th'e two' ends of the furnace are substantially identical in Construction, only one such end accordingly being illustrated in Figs. l and 2. Gas regenerators are used for heating the air as in the aforesaid standard Construction, and the air steam will enter the furnace proper' with nearly uniform velocity in all parts of the passage.

3, and with `all parts approximately parallel to the front and back walls of the furnace as such steam is thence discharged through port opening 4 into the furnace chamber 5 proper.

Extending across the furnace from front to back, underneath this air stream at each end of the hearth, is a removable watercooled brick covered gas pipe 6 with a slot or equivalent line of holes at one siete for a gas outlet. The detail Construction of thi-s pipe will be readily understeod from Fig.` 3, where it will be seen that the concentric jacket 7 completely encloses said' pipe, except for such gas outlet opening 7. The brick 8, in which such water-cooled' pipe is thus embedded, forms the port sill for the opening t, through which the heated air issupplied as aforesaid to the: firiacechamber, and a slo't 9', formed in' such` brick in alignment with the slot in" the pipe', permit's the escape of gas from the Iatter and further assists in directin'gthe gas stream in an" approximately horizontal direction uhdrneath the stream of air. t may be found' desirable' to have such discharge slot 7, and the slot 9 thus aligned therewith, tilted slig'htly downward, but thei important' thing is' to have each' part of the gas stream at the burner outlet as nearly proportional as pos'- si'ble to that part of the' air stream' which lies' directly above it Of course, the simplest ideal condition for this is' such, that if' gas and air streams be considered ascut by a series of equidistant v imaginary planes parallel to the longitudinal aXis of the furnace, each such imaginary section would have a like` proportion of the; total air' flow, a lile proportion of the total gas flow, and therefore the same ratio' of air flow to gas flow and' each such imaginary vertical plane would be parallel to the air and gas streams. In practice, however, the' air stream may well be slightly wider than the gas stream and that portion of the air stream which is near the front and back walls may be slightly slower than the rest thus' to protect these walls. I

In' order to compensate for lack of. uniformity in the rate of flow of the air stream at difi'erent points transversely of port opening 4 due to different frictional resistance encountered and other causes, the slot opening 7' may be initially designed' to' have a corresp'ondin'g variation in width at different" points transversely of the 1111121062- Sin'ce, howev'er, the conditions undercousideration are subject to' change I prefer to provide means such for example, as shown in Figs. 2 and 3` for' adjust-abbz varying the width of the slot opening at different points transversely of the pipe 6, such means in the form illus'trated c'omprising a plural ity of relativel-y short sections 10 of pipe rotata'bl yfitted within said' pip'e 6 in end to end relation, such sections having Slots 11 cut therein of a width equal to or greater than that of' slot 7. A suitable stern' or rod (not shown), operabl'e from one end of the pipe, is adapted to be brought into engagement with said pipe sections 10', and', by' partially rotating them, cut off more or less of the slot 7 and correspondingly reduce the Volume of gas esca ping at this point.

Under the conditions hereinbeiore described, the path of the gas is the resultant of two forces, one due to the direction and linear velocty with which it leaves the burne'r, and the other due to the low specific gravity with respect to the air or products oi' combustion. The path oi the gas thus turns upward, but if there is even a slight eXcess of air, and if the above-described relative distribution of gas and air exists, no considerable portion of the gas can get to the roof without meeting its share of air, and ther'efore being burned'. With low pressu're` and wide gas slot in the burner pipe 6, or with upwarcl tilt of the 'bur-ner opening, the flame will appear short even with no eXcess air; while' with a narrower burner slot and higher pressurc for the same gas flow, the burner being properly tilted` a much longer fiame will be obtained. Of course the flame is also' afiected by the air velocty, but with the above described arrangenent, whereby the ratio of air to gas may be maintained constant, the greater the linear velocty of the air the greater will be the flame length.

The utiliza'tion of my improved design of furnace is not necessarily limited to the case where a relatively rich gas, such as coke oven gas, is employed but is also adaptable,

upon making certain modifications for use with producer gas. Thus, as shown in Fig;

i', the partition 15 between the air slap;

pocket I and gas slag pocket 2 may be carried upwardly and thence forwardly in a general. horizontal direction into the throat of the port 4, such holrizontally extending portion 15 being suitably reinforced by wat'er-cooled' pipes 15 so as to enable same to be made of rclativcly light coustructimi and not take' up too much space in such port cpening. As a' result the producer gas supplied from the gas slag poclret is discharged through a relatively wide low opening boneaththe stream of air, both said gas stream and air stream extending substantially across the entire width of the furna-ce and being, properly proportioncd in relative volumes to give the best results.

In order to give a longer flame and compensatefor insufficient velocty at the main burner, whatever the particular type of the latter, I may place auXil-iary burners in the front and-backwalls of the furnace or in the roof at a point approximately midway between the respective ends of the furnace. One such modified arrangement illustrating the use of auxiliary burners 16 projecting through the furnace walls is shown in Figs. 6 and 7. These transversely disposed auxiliary burners are preferably located below the a'ir stream, and will use up air at difi'erunder most of the excess air.

cnt rates at different distances from the side walls of the furnace. This irregular transverse distribution of air requirement of the auxiliary burners may be Compensated by adjustment of gas distribution at the outlet of the end burner.

The auxiliary burners may, however, be located over the air stream or be adjustable in vertical position, as illustrated in Fig. 8, where a transverse pipe 17, having downwardly directed discharge openings or a slot is shown, said pipe being of a length approximately equal to the transverse width of the furnace and being supported by vertical extensions l'i' at each end, that pass through suitable openings 18 in the furnace roof 19. The pipe 17 and its vertical extensions 17 may be water-cooled and brickcovered. This type of burner is adapted, if desired, to be raised, as ndicated in dotted Outline, into a position directly below the roof 19, Where it will be out of the way during the charging of the furnace, and then may be lowered down. close to the stock and After melting down is completed, this burner may be submerged in the bath, giving a reducing effeet.

The main object sought to be accomi plished by my improved furnace Construction, whatever its particular form, is to introduce the gas mostly under the air stream, with or without contact withthe bath, in such a way that the total gas flow in most of the vertical longitudnal elements of the furnace will be properly proportioned to the total air flow in those elements, thus giving control, not only of heat distribution, but also of oxidizing` or reducing conditions. It will be understood of course that the principle of operation exemplified in my improved furnace Construction is not necessarly limited to an open hearth furnace of the type hereinbefore referred to, but is applicable to other similar types of furnaces; also that liquid hydrocarbon and other tuels that may be introduced in a similar manner may be substituted for the gaseous fuels reterred to above.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the means and the steps heroin disclosed, provided those stated by any one of the following claims or their equivalents be employed.

I therefore particularly point out and distinctly claim as my inventionz-- 1. In a furnace of the character described,

the combination of a hearth, an air port at lel therewith, such fuel supply duct being of approximately the same transverse width as said air port.

2. In a furnace of the character described, the combination of a hearth, an air port at the end thereof extending approximately entirely across said hearth, and a fuel supply duet constructed and arranged to discharge a thin layer of fuel beneath and in a direction substantally parallel with the stream of air from said air port, such tuel supply duct being of approximately the same transverse width as said air port.

In a furnace ofthe character described, the combination of a hearth, an air port at the end thereof extending approximately entirely across said hearth and formed and arranged to dscharge the air thereover in a substantially horizontal direction, and a fuel supply duct formed and arranged to discharge a thin layer of fuel beneath and in a direction substantially parallel with the stream of air from said air port, such fuel supply duet being of approximately the same transverse width as said air port.

a. Ina furance of the character described, the combination of a hearth, an air port at the end thereof extendng approximately entirely across said hearth, and a fuel supply duct constructed and arranged to discharge the fuel beneath the stream of air from said air port and in regulated amounts at different points transversely of said hearth to correspond with the air flow at such points.

5. In a furnace of the character descrbed,

the combination of a hearth, an air port at the end thereof extend'ng approXimately entirely across said hearth, a fuel supply duet having a transverse discharge opening disposed below said air port, and adjustable means adapted to regulate the amount of 'fuel discharged from said duet opening at different points therealong.

6. In a furnace of the character described, the combination of a hearth, an air port at the end thereof extending approximately entirely across said hearth, and a transversely extending gas supply pipe embedded in the sill of said air port, said pipe and sill being formed with aligned openings whereby the gas is discharged in a thin layer beneath the stream of air from said air port.

7.` In a furnace of the character described, the combination of a hearth, an air port at the end thereof extendng appro-Ximately eni tirely across said hearth, and a transversely extending water-cooled gas supply pipe embedded in the sill of said air port, said pipe and sill being formed with aligned opening-s whereby the gas is dscharged in a thin layer beneath the stream of air from said air ort. p 8. In a furnace of the character described, the combinationof a hearth, an air port at the end thereof extending approximately entirely across said hearth, a transversely extively across said hearth, a fnel supply duet constructed and arranged to discharge the fuel beneath the stream of air from said air port, and a supplemental fnel supply duct discharging into said furnace at a point longitudinally spaced from such end. a

10. In a furnace of the character described, the combination of a hearth, an air port at the end thereof extending approximately entirely across said hearth, a fuel supply duet. constructed and arranged to discharge the fuel beneath the stream of air from said air port, and a supplemental fuel supply dnct discharging into said :turnace at a point longitudinally spaced from such end, said supplemental fuel snpply duct being vertically adjustable.

11. In a furnace of the Character described, the combination of a hearth, an air port at the end thereo-f extending' app-roximately entirely across said hearth, a fuel snp-ply duct constructed and arranged to discharge the fuel beneath the stream of air from said air port, and a s'u'pplemental fuel supp-ly duet dischargingr intos'aid furnace at a point longit'udinally spaeed from such end, said Supplement-al fuel supply duc't extending. transversely of said hearth.

12. In a fnrnace of the character described, the c'o-rnbination of a hearth, an air port at the end thereof extending approximately entirely across said hearth, a fuel supply duet constructed and arranged to discharge the fnel beneath the stream of air from said air port, and: a snpplemental fuel supply d-nctdischarging into said furnace at a point longitudinal-ly spaced from such end, said snpplemental fuel supply duetexten'ding transVersel-y of said' hearth and-'being vertically adjustable.

13; In a method of firing an open-health fur'raee, the steps which consist. in introducing a stream of air in an' approximately horizontal direction over* the hearth from one end thereof, such stream extending across the entire width of the heartl r, and d-ischarging the' fu'el beneath such air streamin a layer of approximat'ely` equal transverse width. i i ll. In a method of firing an open-hearth furnace, the' steps* which consist in introdn'cing a stream of air' in an approxinately horizontal direction over the hearth from one end thereof, such stream extending across the entire width of the hearth, and discharging the fuel in a thin transversely extending layer beneath such air stream and in a direction approximately parallel therewith.

15. In a method of firing an open-hearth fnrnace, the steps which consist in introducing a stream of air in an approximately horizontal direction over the hearth from one end thereot, such stream extending across the entire width of the hearth, and discharging the fnel in a thin layer beneath such air stream and in regulated amounts at different transrerse points to correspond approximately with the Volume of air introduced at such points.

16. In a method of firing anopen-hearth f1n'nace,'the steps which consist in introducing stream of air in an approximately horizontal direction over the hearth from one end thereot, such stream extending across the entire width of the hearth, dischargng the main supply of fuel in a thin layer beneath such air' stream, and discharging a supplemental supply of fuel into said furnace at a point longitudin'ally spaced from such end.

17. In a' method of firing an open-hearth turnace, the steps which consist in introducing a stream of air in' an appro'ximately horizontal direction overthe hearth from one end thereof, such stream extending across the entire width of the hearth, discharging the main supply of fuel in a thin layer benea'th such air stream, and discharging' a supplem'ental supply of fuel into said furnace at a point longitu'dinally spaced from such end and at different heights at different stages of operation.

18. In a method of firing an open-hea'rth furnace, the' steps which' consist in introducing a stream of air in an approximately horizontal direction' over the hearth from one end thereof, such stream extending across the entirewidth of the hearth, discharging the main supply of fuel in a' thin layer beneath such air stream, and discharging a supplemental supply of fuel into' said furnace at a point longitudinally spac'e'd from such end and at a decreasing height at successive stages of operation.

19. In a method of ir-ing an open-health furnace, the steps which consist in introducing a stream of air in an approxinately horizontal direction over the hear-th from one end thereor", such stream exten'ding across the entire' width of the hearth, discharging the main supply of fuel in' a thin layer beneath such air stream, and discharging at certain stages in the operation of the' furna'ce a' supplemental supply of fuel directly into the molt'e'n bath in' said furnace at a point longitudinally spaced from' such endi i 20. In a method of firng an open-hearth furnace, the steps which eonsist in introduoing a stream of air in an approximately horizontal direction over the hearth from one end thereo', such stream extendng across the entire Width of the hearth, dsohargng the main supply of fuel in a thin layer beneath such air stream, discharging a supplemental supply of fuel into said furnace at a point longitudnally spaced from such end, and adjustng the trans- Verse distribution of fuel in the main supply to compensate for varyng transverse distribution of air requirement of such suppiemental fuel supply.

Signed by me this 10th day of April,

CALEB DAVIES, JR. 

